He cheated with my best friend

I was in a relationship. It wasn’t a long one. It was nearly 5 months. It was my first boyfriend.

We were both happy at the start of the relationship and we’d see eachother most days. I had a close friend who is younger than both of us, and I soon found out she liked my boyfriend. He promised me nothing was ever going to happen from that and that I was who he wanted and I believed him. A couple of months into the relationship he started hitting me in a playful way but it didn’t seem it. I had bruises for days but didn’t think anything of it at all until after the relationship ended. He’d lie to me about where he was, what he was doing and who he was with and this all just started happening. Again, I didn’t think anything of it.

About a month and a half ago I got a text off him saying he wanted a break, I was heartbroken to say the least, the day after he made the breakup official and I couldn’t see him to even talk to him about it for a week because he was away. My ‘close friend’ was saying to me every minute ‘I can see how much you love him now’ ‘you care about him so much’ etc... Then about a week after that my ex started becoming someone who he wasn’t whilst I was together with him, he started being nasty and accusing me of things and all together just treated me like shit.

A few weeks ago I found out he had had sex with that ‘close friend’ a week after we had broke up. I was completely devastated and heartbroken, I didn’t want to talk to her or him but needed closure in a way. I started to forgive her as it was mainly him that came up with the idea of it happening anyway and now I just feel stupid for that. A couple of days ago I found out he was cheating on me with her whilst I was with him. It happened on multiple occasions and the people that knew (my other friend that I classed as a sister) never told me a thing. I feel betrayed and hurt as I still haven’t had an apology off both my ex or the girl.

Honestly I don’t know what to do, I have fallen out with my other friend as well as she kept such a thing from me but I don’t know weather to forgive her or not. I am not planning on forgiving my ex AT ALL which you probably could imagine and until I get an apology off my ‘close friend’ that old friendship isn’t going to rekindle at all.

I truly just need help on what to do.